This is a three part Phase I/II, open-label trial in HIV-infected infants. The study will examine the antiretroviral activity of three different combination regimens for vertically-infected infants and children age 15 days to #2years: 1) ZDV/3TC/NVP; 2) ZDV/3TC/NVP/1592U89; and 3) d4T/3TC/NVP/NFV. Subjects enrolled into the treatment group containing 1592U89 will be >29 days of age. This study will assess HIV-1 and CD4/ CD8 T-cell kinetics, activation, and maturation. It will also test the concept that early (<3 months of age) use of potent, combination antiretroviral therapy will allow t he long term control of viral replication with preservation of normal immune function. Antiviral activity will be measured primarily by monitoring plasma RNA levels. A total of 24-48 infants and children will be studied. Although the use of these drug combinations includes some with overlapping toxicity profiles (e.g. severe rash, anemia, etc.) the additive risk of these therapies in combination is unknown. However, the limited number of antiretrovirals available for children in this age range, and the chance of controlling HIV being perhaps best in this group with early disease, support the use of the combination therapies proposed in this study.